Refrigeration purge control



May 5, 1964 5 :H ETAL 3,131,548

REFRIGERATION PURSE CONTROL Filed NOV. 1, 1962 SEPARATOR FIG.I

TO PURGE MECHANISM COMPRESSOR DRIVG MOTOR DONALD E. CHUBB WILBUR C.SMITH IN VENTORS H62 I Z 7 United States Patent 3,131,548 REFRIGERATIONPURGE CONTROL Donald E. Chubb, Caldwell, and Wilbur C. Smith,Rutherford, N .J., assignors to Worthington Corporation, Harrison, N.J.,a corporation of Delaware Filed Nov. 1, 1962, Ser. No. 234,638 7 Claims.(Cl. 62-159) This invention relates in general to an improvedrefrigeration system. It relates more particularly to a control meansfor automatically operating a purge arrangement for removingnon-condensible gases from the system.

Closed systems in which a vaporizable refrigerant such as those in theFreon class is normally circulated, depend in large for their efiiciencyon the ability of the system to maintain the refrigerant substantiallyfree of non-condensible gases. Ordinarily, it is impossible tocompletely eliminate air leakage into a closed system operated belowatmospheric pressure so means is provided for purging the entire systemcontinuously or intermittently to remove undesirable gases and maintainthe purity of the refrigerant.

As a feature of economy it is advantageous to purge the systemintermittently rather than continuously. However, to be practical, thepurger must be characterized by simplicity of operation and also beautomatic to avoid the need for continuous monitoring.

It is therefore an object of the present invention to provide anautomatic control means governing operation of a refrigerant purgesystem.

Another object is to provide a closed refrigeration system circulating avaporizable refrigerant and having means for automatically removingnon-condensible gases.

A further object is to provide a method for automatically controllingthe amount of non-condensible gases contained in a closed refrigerationsystem to a minimum.

A still further object is to provide means to automatically operate arefrigeration system purging arrangement responsive to the degree ofsuperheat contained in saturated liquid refrigerant.

These and other objects of the invention will become apparent to oneskilled in the art from the following description made in conjunctionwith the drawings, in which:

FIGURE 1 is a diagrammatic representation of the present closedrefrigeration system including a purge arrangement cooperative with thesystem, and a novel control means for operating the purger.

FIGURE 2 is a diagrammatic representation of the refrigeration systemcondenser shown in FIGURE 1 including an alternate purger control.

The aforementioned objectives are carried out according to the inventionby providing control means cooperative with a first portion of thesystem main condenser holding vaporous refrigerant, together withvariable amounts of non-condensible gases; and a second portion of thesystem holding saturated condensate in contact with its vapor. Thepressure differential between the stated first and second mentionedportions of the system is normally substantially constant. Thus, avariation in the predetermined normal pressure differential, indicatinga pressure build-up attributable to non-condensible gases, will initiateoperation of the purger compressor whereby vapor may be removed from themain condenser and directed to the purging system for separation intothe refrigerant and non-condensibles.

Briefly stated, the invention is hereinafter described in conjunctionwith a refrigeration system holding and circulating a charge of avolatile refrigerant such as CCLBF, and includes a purging meanscooperative with the system for removing non-condensible gases and fordischarging the same to the atmosphere. The basic refrigeration systemconsists of main components including essentially a condenser, acompressor, and an evaporator serially connected by the required valvingto circulate refrigerant at a suificient flow rate to achieve a desiredcooling.

The main condenser, following accepted manufacturing practice, ischaracterized by a vapor holding high pressure chamber, and a hot wellor high pressure receiver which together with the compressor, define thehigh pressure side of the refrigeration system. The normal function ofthe receiver is to accumulate and hold a supply of liquid refrigerant atsaturated condition in a flow chamber substantially at main condenserhead pressure, which liquid is metered to the low pressure mainevaporator through a float controlled mechanism.

The intermittently operated purging arrangement connected to receive airand other non-condensible vapors from the main system, includes a motordriven auxiliary compressor connected to the main condenser vaporholding portion for receiving water, refrigerant, and non-con densiblesin vapor phase. An auxiliary condenser receives hot vapors from thepurge compressor which vapors are condensed and forwarded to an elementin which the liquid is separated from the non-condensibles. Water isfurther separated from the refrigerant, the latter being returned to thesystem for circulation and the water being rejected. Non-condensiblegases are accumulated to a predetermined pressure greater than thesystem pressure and periodically vented to the atmosphere.

The instant control contemplates means whereby the purge compressor isactuated intermittently at such times as the accumulation ofnon-condensibles exceeds a prede termined level. The control means is socommunicated with the main system as to monitor and detect superheat inthe main condenser liquid and to react in response to variationsthereof.

One embodiment of the novel control arrangement includes a conduit meanscommunicated with the high side liquid holding portion of the maincondenser and main evaporator respectively. Flow control meansinterposed in the conduit affords means for varying the flow rate ofsaturated liquid in accordance with main condenser partial pressureattributable to non-condensibles which liquid is subsequentlyrecirculated to the evaporator. Actuating means also disposed in theconduit means is connected for governing operation of the auxiliarypurge compressor motor in response to the increase in partial pressureof non-condensibles in the main condenser vapor holding portion.

Referring to FIGURE 1, a typical refrigeration system is illustratedinto which is incorporated the features of the novel purge controlarrangement. It should be mentioned in passing that the prior art hasdealt considerably with refrigeration systems including gas purgingarrangements. We therefore do not profess to claim novelty in thepresent system of itself, but rather in the novel arrangement andbenefits afforded through use of the automatic control device disposedto be effected by both above mentioned phases of the refrigerationsystem. Also, although the invention has been shown and described asbeing embodied in a particular arrangement of components, it is notintended to so limit the scope of the basic concept which is readilyapplicable to other similarly arranged systems.

Referring more particularly to the figures, the refrigera tion systemand purging arrangement comprise generally: a main refrigerantcompressor ltl connected to and driven by a motor 12. A main condenser14 is communicated with the discharge outlet of compressor 10 throughconduit 15 for introducing hot compressed superheated gas to thecondenser. Condenser 14 includes a hot well 16 or other high pressurereceiver for holding a supply of saturated liquid refrigerant within aflow chamber 17 un- J3 der condenser pressure. Means communicated withthe liquid holding side of high pressure chamber 17 through a floatvalve 19, directs condensed refrigerant through conduit 18 into mainevaporator 21. The closed refrigeration cycle is completed by conduit 22communicating the upper or vapor holding portion of the evaporator withthe inlet of compressor 10.

These main refrigeration elements are standard items in the commercialmarket as is the means for connecting the same to define the closedrefrigeration cycle. Main condenser 14, for example, is provided with acoil 23 circulating a cooling medium such as water for the purpose ofcondensing superheated vapor entering the condenser. The main evaporator21 is similarly provided with a coil 24 through which water iscirculated in heat exchange contact with a bath of liquid refrigerantheld at low pressure in the evaporator to absorb heat upon beingvaporized. This well known arrangement of refrigeration elements in asystem as previously mentioned is old in the art. a purge device in arefrigeration system has similarly been known and utilized for manyyears.

Cooperative with and interconnected to the main refrigeration system isthe purge arrangement. The purger, as shown in FIGURE 1, is constitutedof basic units connected to define a flow circuit including; anauxiliary compressor 26 having a suction inlet 31, a discharge outlet32, and powered by a prime mover 27 such as an electric motor or aninternal combustion engine. Compressor Z6 is connected at inlet 31through an elongated conduit 29 to the upper or vapor'holding portion ofmain condenser 14. This upper portion of the condenser in normaloperation holds refrigerant and water vapors together with the vaporizednon-condensibles which pollute the system. Auxiliary compressordischargeoutlet 32 is communicated through conduit 33 to inlet 35 of anauxiliary condenser 36 shown for the immediate description as being ofthe shell type having an internal coil 34 receiving superheatedcompressed vapors including the aforementioned air which is to be purgedfrom the system.

Compressor motor 27 may be adapted and controlled to run at a suitablespeed to achieve a desired purge rate, alternatively, it may merely runat selected speeds within a particular range. Regulation of motor 27 fordriving the compressor constitutes an important part of the inventionand will be described more thoroughly hereinafter with relation tocontrol of the entire purge system.

The downstream side or outlet 50 of auxiliary condenser 36 is connectedthrough line 37 to the inlet of separator 38 which includes primarilymeans for simultaneously receiving condensed flows of refrigerant andwater from the condenser 36. The separator also receives noncondensiblesfrom the compressor 26 which are dis charged to the atmosphere at anelevated pressure. Discharge of air from separator 33 is ordinarilycontrolled by a pressure sensitive valve 41 or by other means operablein accordance with conditions within the system for maintainingoperating pressure.

Auxiliary compressor 26 may be of a reciprocating or centrifugal typeand suitably coupled to the drive motor 27 which as previously mentionedmay be a constant or variable speed electric motor connected to a powersource, or an internal combustion engine. Compressor 26 normallyfunctions when operated, to compress vapors carried from the vaporholding portion of main condenser 14, which vapors include theundesirable non-condensibles. The auxiliary compressor according to theinvention is started and driven periodically by motor 27 responsive tothe amount of non-condensible gas accumulated in the condenser 14exceeding a minimum predetermined amount. Likewise, this compressor ishalted when purging of the system becomes necessary.

A vaporous stream discharged from compressor 26 is passed through coil34 of auxiliary condenser 36 in which a portion of the vapors receivedis condensed into liquid,

Furthermore, provision of purging means or the non-condensible portionremaining in the vapor phase. Both liquid and vapors are then passedthrough conduit 37 for condenser 36 to separator 38.

The function of the separator is two-fold. Primarily, this elementbifurcates the combined liquid and vaporous stream such that thevaporous air and other gases are accumulated to a predetermined pressureto maintain the pressure within the system, and then vented to theatmosphere through a valve 41. Water and liquid refrigerant are causedto overflow and thus become separated permitting removal of the waterthrough line 42 and recycling of the refrigerant back into the mainsystem. To this end, conduit 43 communicates the liquid holding portionof the separator with the low pressure side of the system at the mainevaporator inlet 44.

An embodiment of control means whereby the instant purger is actuatedfor removing non-condensibles from the system is illustrated in FIGURE 1and consists of the following: conduit 45 communicates the liquidholding high pressure side of main condenser 14 such as the hot well orflow chamber 17 for circulating refrigerant prior to reintroduction intothe low pressure evaporator 21 through conduits 4t), 41 and 46. Conduit45 is provided with a flow constricting orifice 47 having an inletconnected to the downstream end of conduit 45 for passing a restrictedfiow of liquid. Flow control means including a dilferential pressureregulating device 48 positioned downstream of orifice 47 regulates theflow rate of liquid and consequently the pressure in conduit 40 communicating the orifice with the flow control means 48.

Differential pressure element 48 is of standard construction embodyingcharacteristics well known in the art and functions in response to adifferential of at least two pressures applied on a movable element. Onetap 49 is communicated through a fluid holding conduit means 51connected to the vapor containing portion of condenser 14 fortransmitting condenser head pressure. Thus, pressure in this portion ofthe main condenser is normally registered on one side of thedifferential pressure device .-8 urging the flow control element towardone of its operable limits, causing liquid flow through line 4 3 to beincreased in proportion to the increase in pressure in condenser 14. Asecond pressure is communicated with the fiow control element totransmit a force in proportion to the temperature of saturated liquid inhot well 17.

The second actuating pressure is connected to a sensing means 52positioned within the hot well or in the liquid holding flow chamber ofreceiver 17 in which saturated liquid is maintained at a predeterminedlevel prior to passage into evaporator 21.

The sensing means adapted to the present function may suitably be of thetype including a bulb containing expandible liquid, preferably the sameas system refrigerant. Increase in hot well condensate temperature willthus expand the contained liquid eifecting a pressure increasetransmittable to flow control regulator 48.

Under ordinary conditions, when the system operates with a lack ofnon-condensible vapor in condenser 14, there will be only a slightpressure differential between the vapor holding portion of the condenserand the pressure of saturated fluid within the hot well 17. For example,condenser head pressure may normally be on the order of magnitude ofabout 10 to 15 pounds per square inch. The saturated temperature ofliquid in flow chamer 17 under these conditions is within the range ofabout 104 to 113 degrees F. Thus, under varying atmospheric conditions,although the high and low pressures within the vaporized fluidcontaining portion of condenser 14 will vary, the actual pressuredifferential between the vapor portion of the condenser and the liquidholding portion will be substantially constant.

Understandably then, as long as this constant pressure differential ismaintained between the stated points the passage opening of thedifferential pressure valve 48 will be maintained constant. However, asthe amount of noncondensible vapor Within the condenser 14 increasesdue, for example, to air leakage into the system, the partial pressureeffected by such vapor increases the pressure differential at valve 48,increasing liquid flow through line 45, orifice 47 and regulator 48respectively, thus establishing a pressure variable in line 40 from thenorm.

Actuating means 54 positioned in line 40 may be a commercially availableelectrical switch 56, as shown in the figure, normally held in an openposition by pressure within a column 53 communicated with line 40.Pressure in line 40 is thus registered on a diaphragm linked to switch56 for operating the latter. Switch 56 is in turn electrically connectedthrough a suitable relay or starting means, not presently shown, to thepower supply feeding motor 27 whereby the latter is actuated byregulating the electrical input.

The actuating element in its simplest form may embody an electricalswitch, or simply an appropriate mechanical means such as a motiontransmitting linkage controlled by pressure on column 53 when an engineis the prime mover. The linkage is in turn cooperative with the internalcombustion engine through throttle control means for varying the speedof the engine and thus varying the speed of compressor 26. Although thementioned devices as well as other embodiments of the purge controlmeans fall within the broadest concept of the present invention, theprinciple for operating the purger upon the basis of a pressuredifferential at the noted points within a refrigerating system remainsthe same.

For example, while regulating device 48 and actuating mechanism 54 aredescribed as being two distinct elements, it is within the ambit of oneskilled in the art that said elements may be incorporated into a singleunit whereby opening and closing of the liquid passage defined by valve48 may occur simultaneously with the functioning of actuating means 54.

Still another embodiment of the differential sensing means constitutingthe basic function as herein described may consist of a pair of suitablycooperative arms. At least one arm is stationary and carrying one ormore switches while the other arm is movable responsive to conditions inthe circuit, into engagement with the respective switches to controloperation of the purger and compressor motor between the operatinglimits of the movable arm.

Under particular circumstances the main condenser 14 may operate suchthat condensate in the lower portion or in the hot well is at asubcooled condition. This would of course tend to provide an erroneouspressure differential than expected from the refrigerant vapor pressurein the condenser upper or vapor containing portion. With propercondenser design however subcooling of liquid in the hot well may beavoided that a true pressure differential reading is assured.

An alternate arrangement for effecting system purging throughmeasurement of condensate superheat is accomplished in the followingmanner. Referring to FIGURE 2, condenser 14 is provided with acondensate collector 58 supported in the condenser vapor holding portionto receive at least a part of the liquid condensed. Collector 58 may bean open-sided trough, tray or similar receptacle positioned relative tocoil 23 as to catch liquid falling from the coil surface.

Because this liquid pool is positioned in the condenser upper section,saturated liquid will always be subjected to direct condenser pressure.Conduit 60 communicates collector 58 with the condenser hot well 17through a float valve 62 in order that there will always be some liquidstored upon which a superheat measurement might be made. A sensing meansor element 61 is positioned relative collector 58, in contact with theliquid pool held in the latter.

For convenience of manufacture and assembly, conduit 66 may beterminally connected as mentioned but disposed external to the condensershell. When the latter arrangement is employed, the liquid holding meansand sensing element 61 are readily accommodated in a hermetic enclosure.

The sensing element 61 consists of a bulb containing an expandiblefluid. Thus, whether positioned inside or outside of the condenserconfines, the sensing element is always subject to condenser pressure.Element 61 is connected to the purge compressor drive motor through asuitable mechanical or electrical intermediary.

The slightly greater condenser pressure at tray 58 above the pressure ofhot well 17, will promote a steady flow of condensate through line 60and assure a greater accuracy of superheat determination and efficientutilization of the purger.

It is understood that while the present invention is described ascomprising an integral part of a particular refrigeration system, thepurging arrangement and its novel control may be similarly incorporatedinto other forms of refrigeration systems. It is further understood thatcertain modifications and changes may be effected in the control systemWithout departing from the spirit and scope of the invention.

What is claimed is:

1. In a closed refrigeration system circulating a volatile refrigerantand having a main compressor, a main condenser including a cooling coiland having an upper vapor holding portion connected to the maincompressor discharge receiving vaporized refrigerant and non-condensablegases, and having a hot well in the condenser lower portion holdingsaturated refrigerant condensate at condenser pressure:

(a) a purge mechanism connected to and operable with said refrigerationsystem to remove non-condensable gases therefrom,

(b) said purge mechanism including a motor driven auxiliary compressorhaving an inlet communicated with the refrigeration system to receive aflow of both vaporized refrigerant and non-condensable vapors,

(c) a refrigerant condensate collector positioned in the main condenservapor holding pontion, holding a pool of said condensate under condenserpressure,

(d) control means connected to the system to regulate operation of theauxiliary compressor motor and activate said purge mechanism in responseto the volume of non-condensable vapors contained in the refrigerationsystem in excess of a predetermined amount,

(e) said control means including:

(1) sensing means positioned in the condensate collector in contact withthe condensate pool therein,

(2) said sensing means being connected to the purge mechanism auxiliarycompressor motor to regulate operation thereof in response to avariation in pressure in the main condenser vapor holding portion.

2. In a closed refrigeration system substantially as defined in claim 1wherein said refrigerant collector positioned in the main condenservapor holding portion includes:

(a) a tray having an open side disposed downwardly adjacent at least aportion of the main condenser cooling coil to receive condensate fallingfrom the latter.

3. In a closed refrigeration system substantially as defined in claim 1including:

(a) conduit means in communication with the condensate collectorcarrying excessive refrigerant condensate therefrom to maintain acondensate pool in said collector at a predetermined level.

4. In a closed refrigeration system substantially as defined in claim 1wherein the sensing means connected to the purge compressor motorincludes:

(a) a sensing element,

(b) a switch operable in response to actuation of the sensing element,

(c) said switch being connected to a source of power and to saidauxiliary compressor motor for operating the latter in response toconditions in said condensate collector.

5. In a closed refrigeration system having a main evaporator, a maincompressor arranged to receive vapors refrigerant from the mainevaporator, and a main condenser connected to the compressor and havinga high pressure section holding refrigerant vapor and non-con densablegases, said condenser functioning to condense refrigerant vapor forpassage of condensate to the evaporator, a high pressure receiverconnected downstream of the main condenser holding a supply of saidrefrigerant condensate at saturated conditions under main condenser headpressure;

(a) a purge mechanism cooperative with the refrigeration system andincluding a motor driven auxiliary compressor having its suctionconnected to the main condenser high pressure vapor holding section forintermittently receiving said refrigerant and noncondensable gases,

(b) an auxiliary condenser connected to the auxiliary compressordischarge,

(c) conduit means in communication with the supply of condensate in thehigh pressure receiver and passing a stream of said condensate to themain evaporator,

(d) flow control means interposed in said conduit means and beingautomatically adjustable to vary the rate of liquid flow therethrough inresponse to a pressure change in the main condenser high pressuresection, said pressure change being indicative of the presence ofexcessive mon-condensable vapors in the condenser,

(e) sensing means connected to said flow control means to simultaneouslytransmit pressure of said vapor in the condenser vapor holding portion,and the pressure of saturated refrigerant in the high pressure receiver,to the flow control means for effecting automatic adjustment thereof,

(f) a pressure sensitive switch operable by fluid pressure in saidconduits and being movable between first and second positions, saidswitch being connected in respective first and second positions tocontrol operation of the auxiliary compressor motor,

(3) means communicating said switch to pressurized liquid in saidconduit means at a point upstream of the flow control means wherebypressure in said conduit means will effect movement of the switchbetween the first and second positions.

6. In a refrigeration system as defined in claim 5 includi'ng:

(a) means forming a constricted orifice positioned in said conduit meansand being disposed to a position upstream of the flow control means andthe pressure sensative switch respectively.

7. In a closed refrigeration system having a main evaporator, a maincompressor arranged to receive vapor refrigerants from the mainevaporator, and a main condenser connected to the main compressor andhaving a high pressure section holding refrigerant vapor andnoncondensable gases and a first supply of refrigerant condensate in theupper section thereof, said condenser normally functioning to condenserefrigerant vapor for passage of condensate thereof to the evaporator, ahigh pressure receiver downstream of the main condenser and holding asecond supply of refrigerant condensate at saturated conditions undersaid condenser head pressure;

(a) conduit means communicating the second refrigerant supply with themain condenser,

(b) a purge mechanism cooperative with the refrigeration system andincluding a motor driven auxiliary compressor having its suctionconnected to the main condenser high pressure vapor holding section forintermittently receiving said condensed refrigerant and non-condensablegases,

(0) second conduit means communicating the high pressure receiverholding said second condensate supply with the evaporator,

(d) flow control means interposed in said second conduit means and beingautomatically adjustable to vary liquid fiow therethrough in response toa pressure change in the condenser vapor holding high pressure section,said pressure change being indicative of the presence of an excessivenon-condensable vapor in the condenser,

(c) sensing means operably connected with said flow control means andhaving a sensing element positioned in contact with the first condensatesupply to effect adjustment of the flow control means, to simultaneouslytransmit the pressure of vapor in said condenser,

(f) switching means disclosed in said conduit means being movablebetween first and second positions and connected in said respectivepositions to control operation of the auxiliary compressor motor to onand off positions,

(g) said switching means being sensitive to fluid pressure in the secondconduit means at a point upstream of the fiow control means, wherebypressure in said conduit means will effectuate movement of the switchingmeans between said first and second positions for controlling operationsof the compressor motor.

References Cited in the tile of this patent UNITED STATES PATENTS2,298,924 Bichowsky Oct. 13, 1942 2,321,964 Zieber June 15, 19432,577,598 Zwickl Dec. 4, 1951 2,940,274 McGrath June 14, 1960 2,986,894Endress et al June 6, 1961 2,986,905 Kosher et a1 June 6, 1961 3,013,404Endress et a1 Dec. 19, 1961

1. IN A CLOSED REFRIGERATION SYSTEM CIRCULATING A VOLATILE REFRIGERANT AND HAVING A MAIN COMPRESSOR, A MAIN CONDENSER INCLUDING A COOLING COIL AND HAVING AN UPPER VAPOR HOLDING PORTION CONNECTED TO THE MAIN COMPRESSOR DISCHARGE RECEIVING VAPORIZED REFRIGERANT AND NON-CONDENSABLE GASES, AND HAVING A HOT WELL IN THE CONDENSER LOWER PORTION HOLDING SATURATED REFRIGERANT CONDENSATE AT CONDENSER PRESSURE: (A) A PURGE MECHANISM CONNECTED TO AND OPERABLE WITH SAID REFRIGERATION SYSTEM TO REMOVE NON-CONDENSABLE GASES THEREFROM, (B) SAID PURGE MECHANISM INCLUDING A MOTOR DRIVEN AUXILIARY COMPRESSOR HAVING AN INLET COMMUNICATED WITH THE REFRIGERATION SYSTEM TO RECEIVE A FLOW OF BOTH VAPORIZED REFRIGERANT AND NON-CONDENSABLE VAPORS, (C) A REFRIGERANT CONDENSATE COLLECTOR POSITIONED IN THE MAIN CONDENSER VAPOR HOLDING PORTION, HOLDING A POOL OF SAID CONDENSATE UNDER CONDENSER PRESSURE, (D) CONTROL MEANS CONNECTED TO THE SYSTEM TO REGULATE OPERATION OF THE AUXILIARY COMPRESSOR MOTOR AND ACTIVATE SAID PURGE MECHANISM IN RESPONSE TO THE VOLUME OF NON-CONDENSABLE VAPORS CONTAINED IN THE REFRIGERATION SYSTEM IN EXCESS OF A PREDETERMINED AMOUNT, (E) SAID CONTROL MEANS INCLUDING: (1) SENSING MEANS POSITIONED IN THE CONDENSATE COLLECTOR IN CONTACT WITH THE CONDENSATE POOL THEREIN, (2) SAID SENSING MEANS BEING CONNECTED TO THE PURGE MECHANISM AUXILIARY COMPRESSOR MOTOR TO REGULATE OPERATION THEREOF IN RESPONSE TO A VARIATION IN PRESSURE IN THE MAIN CONDENSER VAPOR HOLDING PORTION. 